Mapping a Ternary Carbohydrate Design Space for Stable and Dispersible Protein Dry Powders

Area of Science:

• Materials Science
• Pharmaceutical Sciences
• Biotechnology

Background:

• Optimizing inhalable protein powders requires preserving protein structure and minimizing interparticle cohesion.
• Mechanistic links between excipient composition, drying physics, surface energetics, and aerosol performance are poorly defined.

Purpose of the Study:

• To systematically investigate composition-structure-function relationships in spray-dried lysozyme formulations using a ternary mixture design.
• To elucidate how excipient composition affects protein structure, surface energetics, and aerosol dispersibility.

Main Methods:

• Utilized a constrained ternary mixture design of inulin, trehalose, and mannitol for spray-dried lysozyme formulations.
• Measured protein secondary structure, glass transition temperature, humidity-dependent surface basicity (via inverse gas chromatography), and aerosol dispersibility.
• Analyzed data using linear and quadratic Scheffé mixture models.

Main Results:

• Carbohydrate composition significantly influenced intermolecular β-sheet content and surface basicity.
• Trehalose was associated with increased β-sheet formation, while inulin helped retain surface basicity under humidity.
• A strong inverse relationship was observed between the humidity at minimum surface basicity and aerosol dispersibility (Spearman ρ = -0.86, p = 0.013).

Conclusions:

• Carbohydrate composition dictates protein structural outcomes and aerosol performance through coupled drying and relaxation processes.
• Early moisture-induced surface reorganization correlates with reduced dispersibility.
• Findings provide a mechanistic basis for rational design of inhalable biologic formulations.